The invention relates to a noise barrier pad and the method of manufacturing same for industrial vehicles.
The driver of an industrial vehicle, which as a farm machine for example, is often exposed to exceedingly great noise, which in some cases can be hazardous to his health. In the effort to provide him with working conditions which are satisfactory in this regard, a number of measures have become known, of which the fully enclosed cab is probably the most promising. However, difficulties are created by the fact that, due to the need to bring numerous control levers through the enclosure, it is not possible to exclude entirely the penetration of outside noise, and by the fact that, on the other hand, an acoustical resonant cavity is created between the large glass surfaces which are necessarily involved, which makes it largely impossible to damp out sound waves after they have entered the cavity.
It has already been proposed to provide sound absorbing pads in the roof area or on the unglazed portions of the walls of the cab. However, due to the numerous openings provided for the admission of control levers, and to the fact that the materials are easily harmed by dirt, such pads cannot be used in the lower part of such cabs where the transmission of noise is particularly intense. These areas are therefore generally left unpadded. The effective noise level that has hitherto been achieved is consequently generally close to the maximum limit specified by the trade unions.